Python：使用 len() 根据其他列的值创建新列

Question

My dataframe is a pandas dataframe df with many rows & columns. Now i want to create a new column (series) based on the values of an object column. eg:

df.iloc[0, 'oldcolumn'] Output is 0 should give me 0 in a new column and

df.iloc[1, 'oldcolumn'] Output is 'ab%$.' should give me 5 in the same new column (number of literals incl. space).

in addition, is there a way to avoid loops or own functions? Thank U

Answer 1

To create a new column based on the length of the value in another column, you should do

df['newcol'] = df['oldcol'].apply(lambda x: len(str(x)))

Although this is a generic way of creating a new column based on data from existing columns, Henry's approach is also a good one.

In addition, is there a way to avoid loops or own functions?

I recommend you take a look at How To Make Your Pandas Loop 71803 Times Faster .

Answer 2

You can try this:

df['strlen'] = df['oldcolumn'].apply(len)
print(df)